1. Field of the Invention
The present invention generally relates to braking devices for wheelchairs and similar vehicles. More particularly, this invention relates to a wheelchair braking device having an uncomplicated construction that can be installed on conventional wheelchairs, and which provides a braking action that automatically disengages when an occupant is seated in the wheelchair.
2. Description of the Related Art
Wheelchairs are generally equipped with a brake mechanism to enable the user to more safely enter and leave the seat of the wheelchair. Conventional braking mechanisms typically consist of a pair of levers, each engaging the exterior of one of the larger wheels of the wheelchair. To immobilize the wheelchair, the levers must be manually operated to engage the wheels. While such brake mechanisms are reliable, the operator or user of a wheelchair may forget to engage the lever prior to entering or leaving the seat. If the wheelchair is not properly immobilized by the brake, there is a significant risk of the user falling while trying to stabilize him or herself when entering or leaving the wheelchair.
In response, the prior art has suggested various automatic braking systems for wheelchairs. U.S. Pat. Nos. 3,529,700 to Marshall, U.S. Pat. No. 4,320,818 to Knoche, U.S. Pat. No. 4,623,043 to Babilas, and U.S. Pat. No. 5,203,433 to Dugas teach mechanical braking systems that automatically engage when the user rises off the wheelchair seat. However, these braking mechanisms are relatively complicated and/or require considerable modification to the wheelchair. The use of solenoids to engage and disengage a spring-biased braking lever or pin has also been suggested, as disclosed in U.S. Pat. No. 5,358,266 to Roth et al. However, solenoids and batteries sufficiently powerful to overcome the spring force contribute significantly to the cost of the wheelchair.
An improved wheelchair braking device that overcomes the aforementioned disadvantages is disclosed in commonly-assigned U.S. Pat. No. 5,894,912 to Dobben. Dobben makes use of a lever that senses whether the wheelchair seat is occupied, and a pivoting braking lever biased into engagement with a wheel of the wheelchair to prevent rotation of the wheel and therefore inhibit movement of the wheelchair. The sensing and braking levers are interconnected such that when the wheelchair is occupied, the sensing lever causes the brake lever to rotate out of engagement with the wheel, allowing movement of the wheelchair.
From the above, it can be seen that Dobben provides an automatic braking mechanism that has a relatively uncomplicated and inexpensive construction, and can be readily mounted to a conventional wheelchair without interfering with the operation of the wheelchair. Even so, further improvements would be desirable.